A multi-axis imaging system employing an array of optical imaging elements is a recent development. Related U.S. Patent Application No. 60/276,498; International Patent Application No. PCT/US02/08286; and U.S. Pat. No. 7,061,584, for example, disclose novel method and apparatus for rapidly obtaining an image of an entire slide using an array microscope. In general, this is a multiple-optical-axis, or multi-axis, imaging system having a plurality of imaging elements arranged in an array, each imaging element having one or more optical elements disposed along the optical axis of the array. Where the imaging elements are microscopes, the system is referred to as an Array Microscope (AM), or miniature microscope array (MMA) since the imaging elements are preferably very small.
In a multi-axis imaging system such as an MMA, where the imaging elements are closely packed, constructing a composite image of the entire object that is uniform and artifact-free from images formed by individual objectives remains problematic. In particular, to ensure that every region of the object is imaged, during the scanning operation of the multi-axis MMA, with at least one of the objectives of the objective array of the MMA, these objectives are arranged in a redundant spatial fashion. In particular, the objectives are placed in such a spatial pattern that results in overlapping, in the object plane, of traces across the object of at least some of the fields-of-view (FOVs) of at least some of the objectives. For the purposes of this disclosure, the FOV of an individual imaging in an object space is defined as the projection of an image-plane sensor or a segment of an image-plane sensor (detector) associated with the individual imaging system into the object space, for example into an object plane that is conjugate to the image plane where the image plane detector is located. As a result of the spatial overlapping of the traces of at least some of the FOVs in the object plane, in the image plane the aggregate, initial image formed by the array of objectives includes image portions that contain images of the same object region but by different objectives. Overlapping in the image plane, such image portions are registered twice by the same of the detector pixels and create unwanted artifacts referred to herein as “image overlap”, making it difficult to precisely analyze the object based on the imaging data.
Accordingly, in a situation where, due to hardware constraints, it is problematic to avoid overlapping of the paths of the FOVs that the two individual objectives of the AM trace in the object plane during the scanning operation of the AM, there remains a need to have the AM system appropriately normalized and/or calibrated. The goal of such normalization and/or calibration is to determine which of the detector pixels associated with a region of the image overlap to assign to operating with one of the two objectives, and which remaining pixels to assign to operate with another of the two objectives.